Peanuts

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Most edible nuts, like pecans or hazelnuts, grow on trees. But peanuts grow in pods that mature underground and are classified as a legume, like lentils and peas.

Cashews

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Technically, nuts are a type of fruit. Fruits develop from a plant's ovary, and as the ovary matures it forms a wall around the fruit. For common fruits like apples and peaches, the ovary wall is the fleshy outer skin while for nuts the ovary wall is the hard, outer shell.

Cashews, on the other hand, are a seed of the cashew apple, shown here. The cashew seed is the c-shaped, greyish object at the bottom of the fruit.

Walnuts

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Walnuts are another seed masquerading as a nut. Their shells mature and harden inside of a fibrous, green husk, but it's common to extract the walnut prematurely for the English delicacy pickled walnuts.

Pistachios

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The desert plant called the pistachio tree is a member of the cashew family, and as we've mentioned before: cashews are not a nut. The food that we think of as a pistachio nut, is actually the seed of the pistachio tree, shown here.

Almonds

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Almonds are the seed of the almond tree, which is native to the Middle East and South Asia and is famous for its gorgeous blossoms. In 1890, post-impressionist painter Vincent van Gogh dedicated an entire painting to the almond tree's beauty.